I have had one of these now for about 18 months and it is a great, stable, fast processor. I use processor intensive applications, such as photo-editting, DVD encoding, music-producing (Cubase SX3) and BOINC Projects like Climate Prediction, SETI, Rosetta, World Community Grid and others, which max out your processor to 100% all of the time.
I made the step up from an E6600 - and the Q6600 is basically two of these CPUs bolted together onto one die.
It runs well. It's clockable and I've had no problems with it on my Asus P5W-DH Deluxe mobo. Fast RAM is recommended to get the best out of it.
Great CPU for the price, but as always, will soon be bettered by the new Core i7 chips!!!